Thermal retarder



Feb. 11, 1947. c, M osTERHELD 2,415,522

'mnmm. RETARDER 2 Sheets-Sheet 1 Filed Sept. 20, 1944 I N VEN TOR. CZARX OSE/MAD X ZM ATTORNEY Feb. 11, 1947. c. M. OSTERHELD THERMAL RETARDER Filed Sept. 20, 1944' 2 Sheets-Sheet 2 4 z w m n Z M 1 n M 6 6 CLARA III a ll\ Patented Feb. 11, 1947 THERMAL RETARDER Clark M. Osterheld, Stoughton, Wis., assignor to McGraw Electric Company, Elgin, 111., a corporation of Delaware Application September 20, 1944, Serial No. 555,000

8 Claims.

My invention relates to electric heating and particularly to control devices for the electric heaters of a domestic hot Water tank.

One of the objects of my invention is to provide a relatively simple, inexpensive and easily manufactured control switch structure for selectively causing immediate energization of the electric heater of a domestic hot water tank at the start of an off-peak period and with a predetermined time delay in accordance with the amount of cold water in the tank at the start of the off-peak period.

Other objects of my invention will either be apparent from a description of one form of device embodying my invention, or will be pointed out in the course of such description and set forth particularly in the appended claims.

In the drawings,

Figure 1 is a vertical, sectional view of an ordinary domestic hot water tank, having associated therewith the device embodying my invention,

Fig. 2 is a diagram of the control circuits with the contacts shown in the positions they will occupy when the tank is either entirely full of cold water during an on-peak period, or contains enough cold water to subject the thermal retarder thereto,

Fig. 3 is a diagram of connections similar to Fig. 2, except that the contacts are shown in the positions they will occupy when the tank is at least one-half full of hot water and during an off-peak period,

Fig. 4 is a diagram of control circuits showing the use of an electromagnetic relay to control the retarder time element, with the time-controlled contacts open and with the tank either completely filled with cold water or at least onehalf full of cold water,

Fig. 5 is a top plan view of the improved thermal retarder embodying my invention and shown in Fig. 7,

Fig. 6 is a horizontal, sectional view therethrough, taken on the line 6-6 of Fig. 7,

Fig. 7 is a vertical side elevational view of the thermal retarder with the cover shown in section, and,

Fig. 8 is a front view of Fig. '7.

Referring first of all to Fig. 1 of the drawings, I have there shown an ordinary domestic hot water tank having a lower cold water inlet pipe l3, an upper hot water outlet pipe l5, and being surrounded by a mass ll of heat-insulating material, which latter is held in proper operative position around the tank I by an outer casing I9.

I provide preferably, but not necessarily, a single electric heater 2|, which is shown as being of the clamp-on type and as being located in a tunnel 23 provided around the outside of tank II. If only a single electric heater is used, it is located closely adjacent to the lower end of tank II. All of the hereinbefore mentioned elements of the usual domestic hot water tank installation are old and well known in the art and constitute no part of my present invention.

I provide a lower thermally-actuable heater control switch designated generally by numeral 25, which I have shown as embodying a bimetal bar 21, having one end thereof fixedly mounted on a contact 29, while its other end is adapted to be engaged with and disengaged from a fixed e k contact member 3|. While I have shown a specific form of thermally-actuable heater control switch, I do not desire to be limited thereto and may use any other control switch effective for the same purpose, which is that the switch be in closed position when subject to cold water in the tank and be in open position when subject to hot water in the tank. When I speak of cold water, I mean water the temperature of which is on the order of to F., and when I speak of hot Water, I mean water the temperature of which is on the order of F., or even slightly higher. Switch 25 is effective to open the heater control circuit when substantially all the water in the tank is hot.

Referring now particularly to Figs. 5 to 8, I have there shown my new and improved thermal retarder heater control switch unit, designated generally by numeral 33. This thermal retarder unit is adapted to be mounted in heat-receiving relation on the outside of an ordinary hot water tank, and I prefer to mount it at about the midheight of the tank, although the position thereof may vary slightly from this position. I provide a metallic supporting block 35, the inner surface of which is of arcuate shape to conform to the outer arcuate surface of tank l and I may provide a plurality of welding seams 31 in order to secure the block 35 against the tank The outer surface of block 35 is preferably flat and is adapted to have secured thereagainst a heatconducting bracket 39, which is of substantially L-shape and which may be secured against block 35 by a plurality of short machine screws 4|.

I provide a block 43 of electric-insulating material, which may be of substantially rectangular shape, with a recess 45 therein in its upper surface, adjacent to the outer or front end portion thereof. The block 43 is adapted to be secured against an inner block 4"! of metal and to be held in proper operative position thereagainst as by a plurality of machine screws 49 extending through bracket 33, block 4'! and into block 43. Block 41 may be integral with bracket 39.

Closely adjacent to the inner end portion of block 47 I provide a non-expansible rod 5| having its lower reduced end portion fitting tightly into an opening in block 4! and extending substantially vertically-upwardly parallel to th front surface of bracket 39. I provide further a thermally-expansible rod 53, having its lower reduced end portion also adapted to fit into block 45, the rod 53 extending vertically-upwardly, spaced from and parallel to the non-eXpansible rod .iI. For illustrative purposes, I may here mention that the rod 5| may be made of Invar, a non-expansible steel, while rod 53 may be made of any metal or alloy having the desired degree of expansivity with temperature rise.

The upper end of rod 5! has mounted thereon a pivot block 55 having a horizontal recess 57 therein, which is adapted to receive the upper horizontal arm 59 of a bell crank lever having a vertically-extending arm III. The upper end of the thermally-expansible rod 53 has a slot 63 having a rounded lower surface 65, through which arm 59 extends, so that as rod 53 varies its length because of changes of temperature, the lower end portion of arm El will move in a substantially horizontal path in accordance with the change of length of rod 53. The inner end of arm 59 is mounted on a pivot pin. t1 positioned in member 55.

' I provide switching means actuable by the bell crank lever, operable by the expansion rod 53, this switching means comprising spaced pairs of electrically connected fixed contact members, designated by numerals 63 and II and I3 and I5. Contacts 69 and II are electrically connected with each other, as are contacts I3 and Ill. I provide further a contact bridging member 'I'! adapted to selectively engage with either contacts 39 and 73 or with contacts II and '15.

Contact bridging member I? is adapted to be insulatedly supported in a block I3 of electricinsulating material, which is supported at the lower end of a spring bar 8!, the upper end of which is suitably secured in a slot in the upper end of a supporting member '83, the lower end of which is secured to or is a part of block 43.

When the length of the thermally-expansible rod 53 is a minimum, as when the thermal retarder 33 is subject to cold water, the positions of the switching means will be as shown in Figs. 6 and '7; and when the thermal retarder unit is subject to hot water in the tank and rod 53 has expanded, the contact bridging member TI will be in a position disengaged from the' two pairs of fixed contacts, while when rod 53, or at least one end portion thereof, is at a higher temperature than that of hot water, contact bridging member I! will be in engagement with fixed contacts II and I5.

In order to obtain the higher temperature of an end portion of rod 53 I provide a low-wattage heating coil 85, insulatedly mounted on the upper end of rod 53. In order to provide additional switching means to control the energization of heating coil 85, I provide a pair of contact arms 8'! and 89, the upper end portions of which are positioned in slots in member 83, while the lower end portions are adapted to be positioned just 4 above the upper surface of block 43. The design, construction, and adjustment of contact arms 8'! and 89 are such that contact arm 87 is biased in a clockwise direction, so that it will always be in 5 engagement with an extension 9| on member I9, and contact arm 39 is also biased in a clockwise direction. A stop lug 93, constituting a part of block 43, limits the clockwise movement of contact arm 89, with the result that when thermally- 10 expansible rod 53 is subject to the temperature of cold water in the tank, with attendant engagement of contact bridging member 11 and fixed contacts 69 and 13, contact arm 81 will be in engagement with extension 9i, and contact arm I39 5 will be in engagement with extension 93, so that the contact arms 8! and 89 will be out of engagement with each other. A cover 94 is provided and may be held by a screw.

Referring now to Figs. 2 and 3, I have there shown diagrams of connections of a system, ineluding particularly the thermal retarder shown in Figs. 5 to 8 inclusive. I have shown a timecontrolled switch generally by two contact arms 95 and 91, and this time-controlled switch is controlled by a constantly operative timer, so

that the two contact arms will be in open position and out of engagement with each other during all on-peak periods of a twenty-four hour day, while they will be in closed position and in 3Q engagement with each other during all off-peak periods of a twenty-four hour day. Generally speaking, the off-peak period may extend from say 16 p. m. to about 6 a. m., although I do not desire to be limited thereto.

I provide a pair of supply circuit conductors 9i) and IIII supply circuit conductor 99 being connected to contact arm 93. A conductor I03 connects contact arm 91 with fixed contact I5. A conductor I05 connects contact 75 and contact 13 to one terminal of the heating coil 85, the

other terminal of which is connected by a conductor I91 with contact arm 81 of switch 33.

Contact arm 83 is connected by a conductor I99 with fixed contact II I mounted on block 43, and

contact I I I is connected by a conductor I I3 with contact 3| of the lower thermally-actuable heater control switch 25. Contact III is connected by a conductor II5 to one terminal of heater 2!, the

other terminal of which is connected by a conductor II! to contacts II and 53. Contact 29 of lower thermal switch 25 is connected by a conductor i I9 to the second supply circuit conductor IOI.

The diagram of connections shown in Fig. 2 is that effective when the tank is either entirely full of cold water or is more than half full of cold water, with the result that the thermal retarder 33 is subject to cold water and the contact bridging member I? is in engagement with fixed con- 0 tacts 69 and "I3, thereby closing an energizing circuit through heater 2! as follows, after closure of the time-controlled switch: from supply circuit conductor 99 through engaged contact arms 95 and 9? of the time switch, conductor I33 to contacts l5 and I3, contact bridging member II, contacts 69 and II, through conductor I I1, heater 2|, conductor I I5, closed switch 25, and through conductor I Is to the second supply circuit conductor IfiI. This will cause energization or heater 2|,

70 and assuming that the tank is one-third full of hot water, located in its upper end portion, energization of heater 2| will continue for a period of one .to two hours, until the thermal retarder heater control switch unit is subject to hot water,

76 when the linear expansion of rod 53 will cause disengagement of contact bridging member 11 from contacts 69 and 13, the positions of the various control members then being that shown in Fig. 3 of the drawings. Movement of contact bridging member 11 into the intermediate open position of the switching means has resulted in causing engagement of the contact arms 81 and 89, whereby an energizing circuit through heating coil 85 is closed as follows: from supply circuit conductor 99 through engaged contact arms 95 and 91, conductor I93 to contact 15, through conductor I05, heating coil 85, conductor I01, through engaged contact arms 81 and 89, through conductor I09 to contact I I I, through conductor I I3 to contact 3|, through closed switch 25 to contact 29, and through conductor II9 to the second supply circuit conductor IIlI. The design, construction, and adjustment of the heating coil 85, insulatedly mounted on the upper, outer end portion of rod 53 is such that it will require a length of time on the order of three or four hours before the expansion of the upper end portion of rod 53 is suincient to cause movement of arm BI and the contact bridging member 11 in a counter-clockwise direction and into engagement with contacts H and 15, whereby an energizing circuit is again closed through heater 2I substantially as hereinbefore described, except that now contact bridging member 11 is in engagement with contacts H and 15.

Energization of heater 2| will now continue until substantially all of the water in the tank is hot, if this happens before the end of the off-peak period, when contact arms 95 and 91 will be moved out of engagement with each other, then thermal switch 25 will be moved to open position; or deenergization of heater 2I will be effected by opening movement of contact arms 95 and 91 in case less than substantially all of the water in the tank is hot at the time of opening of the timecontrolled switch at the end of the oil-peak period.

Referring now particularly to Fig. 4 of the drawings, I have there shown a modified form of control circuit embodying an electromagnetic switch, designated generally by numeral I2I, to control the energization of heater 85 on expansion rod 53. The switch I2I comprises a pair of fixed contacts I23 and I25 adapted to be engaged by and disengaged from a contact bridging member I21 insulatedly connected with a magnetizable core member I29, which core member is adapted to be energized by a coil I3 I, which coil is adapted to be traversed by the same current as traverses heater 2I. All of the parts of the system in Fig. 4, which are the same as those shown in Figs. 2 and 3, are provided with like numerals, and only the new or different parts are provided with new numerals. Fixed contacts and 13 are connected by a conductor I33 to one terminal of heating coil 85, the other terminal of which is connected by a conductor I35 to fixed contact I23 of the electromagnetic switch. The other fixed contact I is connected by a conductor I31 to fixed contact 3I. One terminal of heater 2| is connected by a conductor I39 to one terminal of coil I3 I, the other terminal of which is connected by a conductor I4I with fixed contact 69. The one terminal of coil I3I is connected by a conductor I43 with fixed contact 1I. It is to be noted that contacts 69 and 11 are not connected with each other.

Let it now be assumed that the time-controlled switch is closed, as will happen at the start of an off-peak period, and that the tank is more than 6 half full of cold water, with the result that the length of expansion rod 53 is such that contact bridging member 11 will be in engagement with fixed contacts 69 and 13, whereby an energizing circuit is closed through heater 2I as follows: from supply circuit conductor 99 through closed contact arms 95 and 91, through conductor I03 to contacts 15 and 13, through contact bridging member 11 to contact 69, through conductor MI, through coil I3I, through conductor I39, heater 2|, through conductor I I5, through closed switch 25, and through conductor I I9 to the second supply circuit conductor III I. The energized coil I3I will cause upward movement of contact bridging member I21 out of engagement with fixed contacts I23 and I25, whereby energization of heating coil is prevented. After a period on the order of one to two hours, the amount of hot water in the upper part of the tank will have been increased to such an extent that the thermal retarder will be subject to hot water, with the result that bridging member 11 will be moved into its intermediate position out of engagement with either pair of fixed contacts. In this case heater 2I is deenergized and contact bridging member I21 of the electromagnetic switch I2I will move into engagement with contacts I23 and I25, whereby an energizing circuit through heating coil 85 is closed as follows: from supply circuit conductor 99 through engaged contact arms and 91, conductor I03 to contact 15, through conductor I33, heating coil 85, conductor I35, through engaged contacts I23 and I25 with bridging member I21, through conductor I31, closed switch 25, and back through conductor II9 to the second supply circuit conductor IIJI. Thus when the tank is more than half-full of hot water, so that the thermal retarder switch is subject to hot water and the heater is deenergized, the heating coil 85 is energized, with the result that the upper end portion of rod 53 has its temperature raised, so that in say three or four hours contact bridging member 11 will be moved into engagement with contacts H and 15, whereby substantially the same energizing circuit, through heater 2|, as has already been hereinbefore described is closed.

The above discussion started with the assumption that the thermal retarder unit was subject to cold water, with the result that heater 2I was energized immediately upon closure of the time switch at the start of an oil-peak period. Let it now be assumed that only a relatively small amount of hot water was withdrawn from the tank, with the result that only the lower thermally-actuable heater control switch 25 was subject to cold water, with the result that contact bridging member 11 would be in the position shown in Fig. 3 of the drawings, when contact arms 95 and 91 were moved into engagement with each other at the start of an off-peak period. This would result in closing the energizing circuit through heating coil 85 and the attendant result that after a length of time on the order of three or four hours, or say 1 or 2 a. m., energization of heater 2I would be eifected, when contact bridging member 11 was moved into engagement with fixed contacts H and 15. The same comments as made hereinbefore in regard to the termination of the energization of heater 2I apply equally well here, in accordance with whether all of the water in the tank is hot before the end of the off-peak period or whether additional withdrawals of hot Water from the tank during late night hours were made, deenergization of heater 2! would be caused either by the lower thermal switch 25 or by the time-controlled switch.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, and I desire that all such modifications clearly coming within the scope of the appended claims shall be considered as part of my invention.

I claim as my invention:

1. A thermal retarder switch unit for controlling the electric heater of a domestic hot water tank, comprising a thermally-expansible rod adapted to be subject to heat exchange with water in the tank, a switch operated by said rod and having two opposite closed positions and an intermediate open position and means independent of the tank for exchanging heat with a portion of said rod, said switch being adapted to be in its first closed position when the rod is subject to cold water in the tank, to be in open position when the rod is subject to hot water in the tank and to be in its second closed position when a portion of the rod has been heated to an appreciably higher temperature by said heat exchange means.

2. A thermal retarder switch unit for a hot water storage tank heater, comprising a thermally-expansible rod subject to heat exchange with water in the tank, a switch operable by said rod and having two opposite closed positions and an intermediate open position and a heating coil for increasing the temperature of at least an end portion of said rod.

3. A thermal retarder switch unit for a hot water storage tank heater, comprisin a thernm- -finmallyexpansible rod subject to heat exchange with water in the tank, a switch operable by said rod and having two opposite closed positions and an intermediate open position and a heating coil for increasing the temperature of at least an end portion of said rod, the energization of said heating coil being controlled by said rod.

4. A thermal retarder switch unit for hot water storage tank heaters, comprising a thermallyexpansible rod subject to heat exchange'with the water in. the tank, a switch operable by said rod and movable thereby into a first closed position, then into open position, and then into a second closed position, a heating coil for increasing the temperature of an end portion of said rod, a switch for said heating coil and means actuated by said rod for causing closure of said heating coil switch when the switch operable by said rod is in its open position.

5'. A thermal retarder switch unit for a hot water storage tank heater, comprising a thermaliy-expansible rod adapted to be mounted in heat-receiving relation with water in the tank, a switch operable by said rod and having two opposite closed positions and an intermediate open position and a. heating coil for increasing the temperature of an end portion of said rod, said switch being adapted to be in said intermediate open position when subject to hot water in the tank and to move immediately into its first closed position when subject to cold water in the tank and to be moved into its second closed position with a predetermined time period of delay upon energization of said heating coil.

6. A thermal retarder switch unit for a hot water storage tank heater, comprising a thermally-expansible rod adapted to be mounted in heatreceiving relation with water in the tank, a lever arm operatively engaged by said rod, a contact member on said lever arm, at least one pair of spaced fixed contacts adapted to be selectively engaged by said contact member, a heating coil on said rod, a control switch for said heating coil adapted to be held in open position by said lever arm when the rod is subject to cold water in the tank and tobe moved to closed position when said rod is subject to hot water in the tank.

"1. A thermal retarder switch unit for a hot water storage tank heater, comprising a thermally-expansible rod subject to heat exchange with the water in the tank, a heating coil on said rod, a switch operable by said rod having two opposite closed positions and an intermediate open position and being located in said open position when said rod is subject to hot Water in the tank, moved immediately into the first closed position when the rod is subject to cold water in the tank and moved into its second closed position a predetermined length of time after energization of'said heating coil.

8. A thermal retarder switch unit for a hot water storage tank heater, comprising a thermally-expansible rod adapted to have one end portion thereof in heatereceiving relation with water in the tank, switch means operable by said rod having two opposite closed positions and an intermediate open position, a heating coil on the other end portion of said rod for increasing the temperature of said other end portion and means controlled by said rod for causing energization of said heating coil when said switch means is in its intermediate open position.

CLARK M. OSTERHELD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,732,182 Denison Oct, 15, 1929 1,828,692 Townsend Oct. 20, 1931 2,104,848 Clark Jan. 11, 1938 2,304,103 Kelly Dec. 8, 1942 

